Abstract:

A passive pointer device, in shape of a stylus, for being used in
conjunction with a capacitance sensitive touch screen for pointing,
writing, drawing or others on the touch screen.

Claims:

1. A pointer device for being used with a capacitance sensitive touch
screen having a touch sensitive surface, the pointer device comprising:a
conductive pointer tip; anda passive conductive element,wherein said
conductive pointer tip is electrically connected to said passive
conductive element for providing a capacitive disturbance on said touch
sensitive surface when said pointer device touches said surface.

2. The pointer device according to claim 1, wherein said passive
conductive element is a pressure sensing component.

3. The pointer device according to claim 1, wherein said passive
conductive element is a capacitive component.

4. The pointer according to claim 3, wherein said capacitive component is
a piezo electric element.

5. The pointer according to claim 3, wherein said capacitive component is
a piezo electric film.

6. The pointer device according to claim 1, wherein said passive
conductive element is a resistive component.

7. The pointer device according to claim 1, wherein said device further
comprising a casing for housing said pointer tip and said passive
element.

8. The pointer device according to claim 8, wherein the casing is a
regular stylus.

Description:

TECHNICAL FIELD

[0001]The present invention relates in general to a pointer device for
inputting information to an electronic device. More specifically, the
invention relates to a stylus used in conjunction with a capacitance
sensitive touch screen. The present invention also relates to electronic
devices, such as mobile terminals, e.g., mobile telephones, personal
digital assistants (PDAs), digital camera devices and/or handheld
computers, including one or several such input devices.

BACKGROUND ART

[0002]A variety of portable electronic devices, such as mobile terminals
(e.g., mobile telephones, PDA:s, media players and/or handheld
computers), are widely used today. Many of these devices have been
developed to include different object positioning sensing methods and
devices.

[0003]It is known in the field of touch sensitive data input screens,
touch pads, that various object sensing and positioning determining
technologies have been used.

[0004]As an example, pressure sensitive touch pads enabled any object
which could be pressed against a touch pad surface at a localized point
and then moved along the surface as a corresponding movement of a curser
on a computer screen to write a message or input other data. A stylus is
often integrated with the touch pad to provide a pointing device other
than the finger tip, since the stylus provides certain advantages over
the finger tip.

[0005]Capacitive touch screens or pads have been very popular. Good
optical and mechanical performances in combination with good design
possibilities make these touch screens very attractive. This technology
is based on capacitance sensing through a glass screen. A transparent
sensor film is placed behind the glass screen. Upon a finger touch on the
screen a capacitance is created between the finger and the sensor film. A
pattern is created on the sensor film in such a way that coordinates is
provided which corresponds to the position of where the finger touches
the screen. However, one drawback with this is that the use of a finger
or other fairly big conducting objects is needed to detect an input. This
excludes stylus input that is very commonly used with resistive touch
pads.

[0006]Conductive or active styluses with batteries has been shown together
with capacitive touch screens, however the size of these styluses are too
big to be used in a mobile hand sets. It has also been shown to use other
conductive material and induction technology, however this type is also
too big. Active styluses often have to be re-charged or batteries have to
be changed. Further, many of the conductive and/or active styluses of
today are expensive.

SUMMARY OF THE INVENTION

[0007]With the above and following description in mind, then, an aspect of
some embodiments of the present invention is to provide a passive input
device that can be used on a capacitive touch panel, which seeks to
mitigate, alleviate or eliminate one or more of the above-identified
deficiencies in the art and disadvantages singly or in any combination.

[0008]An aspect of the present invention relates to a pointer device for
being used with a capacitance sensitive touch screen having a touch
sensitive surface. The pointer device comprises a conductive pointer tip
and a passive conductive element. Further, the conductive pointer tip is
electrically connected to the passive conductive element for providing a
capacitive disturbance on the touch sensitive surface when the pointer
device touches the surface.

[0009]In one embodiment the passive conductive element may be a pressure
sensing component.

[0010]In another embodiment the passive conductive element may be a
capacitive component. The capacitive component may be a piezo electric
element or a piezo electric film.

[0011]In a further embodiment the passive conductive element may be a
resistive component.

[0012]In still a further embodiment the pointer device may comprise a
casing for housing the pointer tip and the passive element. The casing
may be a regular stylus.

[0013]The features of the above-mentioned embodiments can be combined in
any combinations.

[0014]Some embodiments of the invention provide a pointer device for
capacitive sensing touch screens. It is an advantage with some
embodiments of the invention that they may allow for getting the
advantages of a capacitive touch panel and still keep a stylus which may
be used as a pointer on a capacitive sensing touch screen without any
active components that needs to be changed. It is another advantage with
some embodiments of the invention that they may allow for providing an
improved user experience and a good looking mobile hand set with a slim
pointer device. Another advantage with some embodiment of the present
invention is that since a piezo element may be small and stacked, it may
easily be built into a regular stylus. Still another advantage with some
embodiment of the present invention is that if the user looses the
pointer device of the present invention the user may still be able to use
the finger as a pointer device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]Further objects, features and advantages of the present invention
will appear from the following detailed description of the invention,
wherein embodiments of the invention will be described in more detail
with reference to the accompanying drawings, in which:

[0017]FIG. 2 illustrates a pointer device according to an embodiment of
the present invention;

[0018]FIG. 3a-b illustrates a pointer device according to an embodiment of
the present invention.

DETAILED DESCRIPTION

[0019]Embodiments of the present invention relate, in general, to the
field of pointer devices used in conjunction with capacitive touch
screens. A preferred embodiment relates to a passive pointer device, in
shape of a stylus, used for pointing, writing, drawing or others on a
capacitive touch screen.

[0020]Embodiments of the present invention will be described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may, however, be
embodied in many different forms and should not be construed as limited
to the embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and will
fully convey the scope of the invention to those skilled in the art. Like
reference signs refer to like elements throughout.

[0021]One example of a capacitive touch screen 20 is shown in FIG. 1. The
touch screen may comprise a substrate (not shown) on which a conductive
sensing layer 1 is coated. The substrate may be coated with a conductive
layer, typically indium tin oxide or, alternatively, copper that is
capable of conducting a continuous electrical current across the
conductive layer. The capacitive touch screen 20 may therefore exhibit a
controlled field of stored electrons in both horizontal and vertical
axes--it achieves capacitance. The human body is also an electronic
device which has stored electrons and, therefore, also exhibits
capacitance. When the `normal` capacitance field (i.e. reference state)
of the capacitive touch screen 20 is altered by another capacitance
field, e.g., someone's finger 5, electronic circuits of capacitive touch
screen 20 may measure the resultant distortion in the sine wave
characteristics of the reference capacitance field or in another common
way. A controller included in the electronic device, in which the touch
screen 20 is included may receive the information of the resultant
distortion in the sine wave characteristics of the reference field for
operational processing. The capacitive touch screen 20 can be touched by
a bare finger or with a conductive device 5 being held by a bare hand.
However, the capacitive touch screen 20 is not affected by outside
objects such as a tip of a pencil or other similar object.

[0022]With reference to FIG. 1, a capacitive touch screen 20 may detect a
fairly large conducting object such as a finger 5 or other large
conductive objects. The transparent sensor layer 1 is placed behind a
glass screen 2. Upon a finger touching the screen a capacitance is
created between the finger 5 and the sensor layer 1. A pattern, a sensing
grid, is created on the sensor layer 1 in such a way that coordinates may
be provided which corresponds to the position of where the finger touches
the screen.

[0023]The sensing layer 1 includes driving lines 4 that supply voltage and
detection lines 3 which detect voltage changes. The finger 5 acts as
ground when touching the screen close to the sensing layer 1 and an
Electrical magnetic field, E-field, is generated between the driving line
4 and the finger 5. This E-field is detected by the detecting line 3
which generates a signal. By scanning several lines in the sensing grid
on the sensing layer 1 the present position of the finger on the screen
may be calculated, i.e. by a CPU in the electronic device comprising the
touch screen.

[0024]The herein below presented various embodiments of the invention uses
a pressure sensing device and a conductive contact device 7, 8. As will
be described further herein, this use of both a pressure sensing device
and a conductive contact device provides for an improved pointer device,
which is suitable for being used in conjunction with a capacitive touch
screen.

[0025]FIG. 2 illustrates a first embodiment of a pointer device 6
according to the invention. The pointer device comprises a conductive
contact device 8 and a pressure sensing device 7 mounted in a casing 9,
such as a regular stylus casing or the like.

[0026]In the embodiment shown in FIG. 2, the contact device 8 is a metal
pen-tip. The contact device 8 is configured to provide a capacitance
disturbance in the sensing layer 1 in a touch screen 20 when the user
touches or presses the contact device 8 against the touch screen.

[0027]The metal pen-tip may be covered by a cover layer, to protect the
touch screen when using the pointer device. The cover layer may be made
of, e.g., plastic, rubber, etc.

[0028]The pressure sensing device 7 comprised in this embodiment is in the
form of a piezo element. A piezo element may be a ceramic component or a
film with piezo electric properties.

[0029]The pen tip 8 and the piezo element 7 are electrically connected. As
can be seen in FIGS. 3a and 3b, the piezo element 7 is positioned
relative to the pen-tip 8 such that, upon depression of the pointer
device 6 against the touch screen 20, the pen-tip 8 actuates towards the
piezo element 7, as illustrated by the arrows in FIG. 3b, for depressing
the piezo element 7. The piezo element 7 generates voltage upon
mechanical impact and the pen-tip will be charged by the piezo element
and a capacitance between the pen-tip 8 and the detecting line 3 in the
sensor layer 1 of the touch screen is created. The applied voltage on the
pen tip 8 generates an E-field over the capacitance sufficient to detect
a voltage change on the detecting line 3 and thus generate a signal. The
grid of detecting lines is scanned as before which gives position of the
stylus.

[0030]In a very simplified electrical model 10, as shown in FIG. 2, the
piezo element within the stylus may be seen as a voltage source 12 and
the gap between sensor layer 1 and pen-tip 8 may be seen as a capacitance
source 13 and the user holding the pointer device act as ground 11.

[0031]In use, a user of the tip of the pointer device is placing the tip
in contact with the touch screen surface and a capacitive disturbance is
created on the touch screen. Additionally, the user of the pointer device
is moving the pointer device over the touch screen, such as when the user
write or "draw" on the touch screen, and the touch screen is sensing the
pointer device moving across the screen and recognizing characters,
numbers or other data inputs by using appropriate software and hardware.

[0032]The pointer device may also comprise some additional passive
electrical components or some mechanical components, e.g. mechanical
spring, for improving/optimizing the performance of the pointer device.

[0033]The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the
invention. As used herein, the singular forms "a", "an" and "the" are
intended to include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" "comprising," "includes" and/or "including" when used herein,
specify the presence of stated features, integers, steps, operations,
elements, and/or components, but do not preclude the presence or addition
of one or more other features, integers, steps, operations, elements,
components, and/or groups thereof.

[0034]Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this invention
belongs. It will be further understood that terms used herein should be
interpreted as having a meaning that is consistent with their meaning in
the context of this specification and the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly so
defined herein.

[0035]The foregoing has described the principles, preferred embodiments
and modes of operation of the present invention. However, the invention
should be regarded as illustrative rather than restrictive, and not as
being limited to the particular embodiments discussed above. The
different features of the various embodiments of the invention can be
combined in other combinations than those explicitly described. It should
therefore be appreciated that variations may be made in those embodiments
by those skilled in the art without departing from the scope of the
present invention as defined by the following claims.